Ecological problems of the Amu Darya delta

Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 3, pp. 6–8, March, 1992.     

A comparison of several approximations to the power function of the likelihood ratio test in covariance structure analysis*

In this paper we compare alternative asymptotic approximations to the power of the likelihood ratio test used in covariance structure analysis for testing the fit of a model. Alternative expressions for the noncentrality parameter (ncp) lead to different approximations to the power function. It appears that for alternative covariance matrices close to the null hypothesis, the alternative ncp's lead to similar values, while for alternative covariance matrices far from H_o the different expressions for the ncp can conflict substantively. Monte Carlo evidence shows that the ncp proposed in Satorra and Saris (1985) gives the most accurate power approximations.     

Book review

CLIMATIC FLUCTUATIONS AND WATER MANAGEMENT. by M. A. Abu‐Zeid and A. K. Biswas Butterworth Heinemann, Oxford, 1992, 356 pp, £50.00.     

AN EMPIRICAL INVESTIGATION INTO THE IMPACT OF PROFIT SHARING SCHEMES OF EXECUTIVIES ON THE CONTENT OF CORPORATE SUBMISSIONS ON PROPOSED ACCOUNTING STANDARDS

This paper examines the comments submitted by UK companies on 20 proposed accounting standards to test the hypotheses that executives favor standards that increase, or dampen the variance of, accounting profit numbers on which their incentive remuneration is based. Test results were generally as hypothesised but only the profit variance outcomes were statistically significant. Allowing for political environment changes affected only the profit variance results. There was no evidence that the relative monetary size of bonus payments was a significant lobbying factor. No significant differences were found between the lobbying preferences of companies with or without executive incentive schemes.     

CAN INEFFICIENT TRADERS CREATE VALUE?

I examine the aggregate expected profit generated by informed traders of diverse ability in a competitive market. I assume that efficient traders get perfect information on asset values whereas inefficient traders get noisy information. In the presence of order size restrictions, I show that the aggregate expected profit generated by efficient and inefficient traders together can be higher than that generated by efficient traders alone. Thus, inefficient traders can create value in a constrained trading environment.     

Floc size distribution in a stirred suspension.

This paper focuses on the distribution of alumino-humic flocs found in a stirred suspension. Distributions were scaled using the transformation u = d/dL in which d is floc diameter and dL its arithmetic mean value and fitted by a gamma distribution. Flocs were treated as monofractal with solids mass concentration specified by C = A'rhos (d/do)D-3 in which A' is a packing coefficient, rhos the density of the floc solids, D the fractal dimension and do a reference size. It was shown that the overall solids concentration (M) complies with the dependence M proportional to NA'dDL-S(D) in which N is the number of flocs per unit volume and S(D) a distribution moment. Initial estimates of A' and D were obtained from analysis of floc sedimentation behaviour. From knowledge of the base parameters, the calculated value of M did not match the measured M and varied with shear. This was attributed to a kinematic influence on C over and beyond changes associated with the response of dL to shear. Issues of self-similarity were examined and it was concluded that distributions did not display strict self-similarity. Data are provided on the size distribution found in the flocculators of a treatment works at full scale.     

Hydrogen-driven denitrification of wastewater in an anaerobic submerged membrane bioreactor: potential for water reuse.

An anaerobic submerged membrane bioreactor was coupled with a novel hydrogen delivery system for hydrogenotrophic denitrification of municipal final effluent containing nitrate. The biological treatment unit and hydrogen delivery unit were proven successful in removing nitrate and delivering hydrogen, respectively. Complete hydrogen transfer resulted in reducing nitrate below detectable levels at a loading of 0.14 kg Nm(-3) d(-1). The produced water met all drinking water guidelines except for color and organic carbon. However, the organic carbon was removed by 72% mostly by membrane rejection. To reduce the organic carbon and color of the effluent, post treatment of the produced water is required.     

The Impact of Regulation Fair Disclosure on Information Asymmetry and Trading: An Intraday Analysis

This study examines the impact of Regulation Fair Disclosure (FD) on liquidity, information asymmetry, and institutional and retail investors trading behavior. Our main findings suggest three conclusions. First, Regulation FD has been effective in improving liquidity and in decreasing the level of information asymmetry. Second, retail trading activity increases dramatically after earnings announcements but there is a significant decline in institutional trading surrounding earnings announcements, particularly in the pre‐announcement period. Last, the decline in information asymmetry around earnings announcements is closely associated with a lower participation rate in the pre‐announcement period and more active trading of retail investors after earnings releases.     

Bayesian MCMC Mapping of Quantitative Trait Loci in a Half-sib Design: a Graphical Model Perspective

Graphical models provide a powerful and flexible approach to the analysis of complex problems in genetics. While task-specific software may be extremely efficient for any particular analysis, it is often difficult to adapt to new computational challenges. By viewing these genetic applications in a more general framework, many problems can be handled by essentially the same software. This is advantageous in an area where fast methodological development is essential. Once a method has been fully developed and tested, problem-specific software may then be required. The aim of this paper is to illustrate the potential use of a graphical model approach to genetic analyses by taking a very simple and well-understood problem by way of example.